Mike Mountain Horse was a scout and interpreter for the Royal North West Mounted police. During the First World War he served in the Canadian Expeditionary Force, fighting at Vimy Ridge, Hill 70, Cambrai, and Amiens.

Wounded three different times, he once led a machine gun section of his battalion behind enemy defences. He was injured and buried alive when an enemy shell demolished their shelter. It was four days before he was discovered.

He was awarded a Distinguished Conduct Medal for his bravery on the battlefield and at the end of the War was demobilized as an acting Sergeant.